The present invention relates to an image reading system
Generally, as an image reading system for reading an original such as a photograph, a document, etc., an image scanner, an electronic copying apparatus, a facsimile, etc. are known.
In such image reading system, first the size and orientation of an original that is put on an original table are detected, and then reading control, selection of a print paper, etc. are executed based on the detected size and orientation of the original.
As the means for detecting the size and orientation of the original, the means disclosed in Patent Application Hei 4-34200 (Japanese Patent No. 3168666), for example, is employed. The size and orientation of the original can be decided based on a length of the original in the main scanning direction and presence/absence of the original at predetermined positions on the original table. Therefore, in the means disclosed in Patent Application Hei 4-34200 (Japanese Patent No. 3168666), the length of the original in the main scanning direction is detected by a linear image sensor that is used to read the original, while the presence/absence of the original at the predetermined positions on the original table is detected by an optical sensor and light source, both are provided separately from the linear image sensor used to read the original and the light source respectively. Since the optical sensor is provided separately, detecting of the length of the original in the main scanning direction and detecting of the presence/absence of the original can be simultaneously executed. Thus, the size and orientation of the original can be detected in a short time.
As another means for detecting the size and orientation of the original, first the length in the main scanning direction is detected by using the linear image sensor used to read the original, then a carriage on which an optical system for focusing an optical image onto the linear image sensor is mounted is moved in the sub scanning direction, and then the presence/absence of the original at the predetermined positions is detected by using such linear image sensor. Thus, the size and orientation of the original can be detected without the provision of another optical sensor and another light source.
However, if the optical sensor and the light source are provided separately to detect the presence/absence of the original at the predetermined positions on the original table, such a problem is caused that a production cost of the image reading system is increased. In contrast, if the length in the main scanning direction and the presence/absence of the original at the predetermined positions on the original table are defected by moving the carriage while using one linear image sensor, there is no necessity that the optical sensor and the light source should be provided separately, nevertheless such problems are caused that the length in the main scanning direction and the presence/absence of the original at the predetermined positions cannot be detected simultaneously and it takes a lot of time to detect the size and orientation of the original.